De Re Metallica Part 22

The German words obviously had local value and do not bear translation literally.

[3] One _metreta_, a Greek measure, equalled about nine English gallons, and a _congius_ contained about six pints.

[4] _Ingestores_. This is a case of Agricola coining a name for workmen from the work, the term being derived from _ingero_, to pour or to throw in, used in the previous clause--hence the "reason." See p. x.x.xi.

[5] _Cisium_. A two-wheeled cart. In the preface Agricola gives this as an example of his intended adaptations. See p. x.x.xi.

[6] _Canis_. The Germans in Agricola's time called a truck a _hundt_--a hound.

[7] _Alveus_,--"Tray." The Spanish term _batea_ has been so generally adopted into the mining vocabulary for a wooden bowl for these purposes, that we introduce it here.

[8] Pliny (x.x.xIII., 21). "The fragments are carried on workmen's shoulders; night and day each pa.s.ses the material to his neighbour, only the last of them seeing the daylight."

[10] _Harpago_,--A "grapple" or "hook."

[11] Ancient Noric.u.m covered the region of modern Tyrol, with parts of Bavaria, Salzburg, etc.

[12] _Machina quae pilis aquas haurit_. "Machine which draws water with b.a.l.l.s." This apparatus is identical with the Cornish "rag and chain pump" of the same period, and we have therefore adopted that term.

[13] A _congius_ contained about six pints.

[14] Vitruvius (X., 9). "But if the water is to be supplied to still higher places, a double chain of iron is made to revolve on the axis of the wheel, long enough to reach to the lower level. This is furnished with brazen buckets, each holding about a _congius_. Then by turning the wheel, the chain also turns upon the axis and brings the buckets to the top thereof, on pa.s.sing which they are inverted and pour into the conduits the water they have raised."

[15] This description certainly does not correspond in every particular with the ill.u.s.tration.

[16] There is a certain deficiency in the hydraulics of this machine.

[17] The dimensions given in this description for the various members do not tally.

[18] _Melibocian_,--the Harz.

[19] In the original text this is given as "lower," and appears to be an error.

[20] Pliny (x.x.xI, 28). "In deep wells, the occurrence of _sulphurata_ or _aluminosa_ vapor is fatal to the diggers. The presence of this peril is shown if a lighted lamp let down into the well is extinguished. If so, other wells are sunk to the right and left, which carry off these noxious gases. Apart from these evils, the air itself becomes noxious with depth, which can be remedied by constantly shaking linen cloths, thus setting the air in motion."

[21] This is given in the German translation as _kobelt_. The _kobelt_ (or _cobaltum_ of Agricola) was probably a.r.s.enical-cobalt, a mineral common in the Saxon mines. The origin of the application of the word cobalt to a mineral appears to lie in the German word for the gnomes and goblins (_kobelts_) so universal to Saxon miners' imaginations,--this word in turn probably being derived from the Greek _cobali_ (mimes). The suffering described above seems to have been a.s.sociated with the malevolence of demons, and later the word for these demons was attached to this disagreeable ore. A quaint series of mining "sermons," by Johann Mathesius, ent.i.tled _Sarepta oder Bergpostill_, Nurnberg, 1562, contains the following pa.s.sage (p. 154) which bears out this view. We retain the original and varied spelling of cobalt and also add another view of Mathesius, involving an experience of Solomon and Hiram of Tyre with some mines containing cobalt.

"Sometimes, however, from dry hard veins a certain black, greenish, grey or ash-coloured earth is dug out, often containing good ore, and this mineral being burnt gives strong fumes and is extracted like 'tutty.' It is called _cadmia fossilis_. You miners call it _cobelt_. Germans call the Black Devil and the old Devil's furies, old and black _cobel_, who injure people and their cattle with their witchcrafts. Now the Devil is a wicked, malicious spirit, who shoots his poisoned darts into the hearts of men, as sorcerers and witches shoot at the limbs of cattle and men, and work much evil and mischief with _cobalt_ or _hipomane_ or horses' poison. After quicksilver and _rotgultigen_ ore, are _cobalt_ and _wis.m.u.th_ fumes; these are the most poisonous of the metals, and with them one can kill flies, mice, cattle, birds, and men. So, fresh _cobalt_ and _kisswa.s.ser_ (vitriol?) devour the hands and feet of miners, and the dust and fumes of _cobalt_ kill many mining people and workpeople who do much work among the fumes of the smelters. Whether or not the Devil and his h.e.l.lish crew gave their name to _cobelt_, or _kobelt_, nevertheless, _cobelt_ is a poisonous and injurious metal even if it contains silver. I find in I. Kings 9, the word _Cabul_. When Solomon presented twenty towns in Galilee to the King of Tyre, Hiram visited them first, and would not have them, and said the land was well named _Cabul_ as Joshua had christened it. It is certain from Joshua that these twenty towns lay in the Kingdom of Aser, not far from our _Sarepta_, and that there had been iron and copper mines there, as Moses says in another place. Inasmuch, then, as these twenty places were mining towns, and _cobelt_ is a metal, it appears quite likely that the mineral took its name from the land of Cabul. History and circ.u.mstances bear out the theory that Hiram was an excellent and experienced miner, who obtained much gold from Ophir, with which he honoured Solomon.

Therefore, the Great King wished to show his grat.i.tude to his good neighbour by honouring a miner with mining towns. But because the King of Tyre was skilled in mines, he first inspected the new mines, and saw that they only produced poor metal and much wild _cobelt_ ore, therefore he preferred to find his gold by digging the gold and silver in India rather than by getting it by the _cobelt_ veins and ore. For truly, _cobelt_ ores are injurious, and are usually so embedded in other ore that they rob them in the fire and consume (_madtet und frist_) much lead before the silver is extracted, and when this happens it is especially _speysig_. Therefore Hiram made a good reckoning as to the mines and would not undertake all the expense of working and smelting, and so returned Solomon the twenty towns."

[22] Pliny (x.x.xIII, 40). "Those employed in the works preparing vermilion, cover their faces with a bladder-skin, that they may not inhale the pernicious powder, yet they can see through the skin."

[23] _Pompholyx_ was a furnace deposit, usually mostly zinc oxide, but often containing a.r.s.enical oxide, and to this latter quality this reference probably applies. The symptoms mentioned later in the text amply indicate a.r.s.enical poisoning, of which a sort of spherical effect on the hands is characteristic. See also note on p. 112 for discussion of "corrosive" _cadmia_; further information on _pompholyx_ is given in Note 26, p. 394.

[24] Orcus, the G.o.d of the infernal regions,--otherwise Pluto.

[25] Caius Julius Solinus was an unreliable Roman Grammarian of the 3rd Century. There is much difference of opinion as to the precise animal meant by _solifuga_. The word is variously spelled _solipugus, solpugus, solipuga, solipunga_, etc., and is mentioned by Pliny (VIII., 43), and other ancient authors all apparently meaning a venomous insect, either an ant or a spider. The term in later times indicated a scorpion.

[26] The presence of demons or gnomes in the mines was so general a belief that Agricola fully accepted it. This is more remarkable, in view of our author's very general scepticism regarding the supernatural. He, however, does not cla.s.sify them all as bad--some being distinctly helpful. The description of gnomes of kindly intent, which is contained in the last paragraph in _De Animantibus_ is of interest:--

"Then there are the gentle kind which the Germans as well as the Greeks call cobalos, because they mimic men. They appear to laugh with glee and pretend to do much, but really do nothing. They are called little miners, because of their dwarfish stature, which is about two feet. They are venerable looking and are clothed like miners in a filleted garment with a leather ap.r.o.n about their loins. This kind does not often trouble the miners, but they idle about in the shafts and tunnels and really do nothing, although they pretend to be busy in all kinds of labour, sometimes digging ore, and sometimes putting into buckets that which has been dug. Sometimes they throw pebbles at the workmen, but they rarely injure them unless the workmen first ridicule or curse them. They are not very dissimilar to Goblins, which occasionally appear to men when they go to or from their day's work, or when they attend their cattle.

Because they generally appear benign to men, the Germans call them _guteli_. Those called _trulli_, which take the form of women as well as men, actually enter the service of some people, especially the _Suions_.

The mining gnomes are especially active in the workings where metal has already been found, or where there are hopes of discovering it, because of which they do not discourage the miners, but on the contrary stimulate them and cause them to labour more vigorously."

The German miners were not alone in such beliefs, for miners generally accepted them--even to-day the faith in "knockers" has not entirely disappeared from Cornwall. Neither the sea nor the forest so lends itself to the substantiation of the supernatural as does the mine. The dead darkness, in which the miners' lamps serve only to distort every shape, the uncanny noises of restless rocks whose support has been undermined, the approach of danger and death without warning, the sudden vanis.h.i.+ng or discovery of good fortune, all yield a thousand corroborations to minds long steeped in ignorance and prepared for the miraculous through religious teaching.

[27] The Plains of Laurentius extend from the mouth of the Tiber southward--say twenty miles south of Rome. What Agricola's authority was for silver mines in this region we cannot discover. This may, however, refer to the lead-silver district of the Attic Peninsula, Laurion being sometimes Latinized as _Laurium_ or _Laurius_.

BOOK VII.

Since the Sixth Book has described the iron tools, the vessels and the machines used in mines, this Book will describe the methods of a.s.saying[1] ores; because it is desirable to first test them in order that the material mined may be advantageously smelted, or that the dross may be purged away and the metal made pure. Although writers have mentioned such tests, yet none of them have set down the directions for performing them, wherefore it is no wonder that those who come later have written nothing on the subject. By tests of this kind miners can determine with certainty whether ores contain any metal in them or not; or if it has already been indicated that the ore contains one or more metals, the tests show whether it is much or little; the miners also ascertain by such tests the method by which the metal can be separated from that part of the ore devoid of it; and further, by these tests, they determine that part in which there is much metal from that part in which there is little. Unless these tests have been carefully applied before the metals are melted out, the ore cannot be smelted without great loss to the owners, for the parts which do not easily melt in the fire carry the metals off with them or consume them. In the last case, they pa.s.s off with the fumes; in the other case they are mixed with the slag and furnace accretions, and in such event the owners lose the labour which they have spent in preparing the furnaces and the crucibles, and further, it is necessary for them to incur fresh expenditure for fluxes and other things. Metals, when they have been melted out, are usually a.s.sayed in order that we may ascertain what proportion of silver is in a _centumpondium_ of copper or lead, or what quant.i.ty of gold is in one _libra_ of silver; and, on the other hand, what proportion of copper or lead is contained in a _centumpondium_ of silver, or what quant.i.ty of silver is contained in one _libra_ of gold.

And from this we can calculate whether it will be worth while to separate the precious metals from the base metals, or not. Further, a test of this kind shows whether coins are good or are debased; and readily detects silver, if the coiners have mixed more than is lawful with the gold; or copper, if the coiners have alloyed with the gold or silver more of it than is allowable. I will explain all these methods with the utmost care that I can.

The method of a.s.saying ore used by mining people, differs from smelting only by the small amount of material used. Inasmuch as, by smelting a small quant.i.ty, they learn whether the smelting of a large quant.i.ty will compensate them for their expenditure; hence, if they are not particular to employ a.s.says, they may, as I have already said, sometimes smelt the metal from the ore with a loss or sometimes without any profit; for they can a.s.say the ore at a very small expense, and smelt it only at a great expense. Both processes, however, are carried out in the same way, for just as we a.s.say ore in a little furnace, so do we smelt it in the large furnace. Also in both cases charcoal and not wood is burned. Moreover, in the crucible when metals are tested, be they gold, silver, copper, or lead, they are mixed in precisely the same way as they are mixed in the blast furnace when they are smelted. Further, those who a.s.say ores with fire, either pour out the metal in a liquid state, or, when it has cooled, break the crucible and clean the metal from slag; and in the same way the smelter, as soon as the metal flows from the furnace into the forehearth, pours in cold water and takes the slag from the metal with a hooked bar. Finally, in the same way that gold and silver are separated from lead in a cupel, so also are they separated in the cupellation furnace.

It is necessary that the a.s.sayer who is testing ore or metals should be prepared and instructed in all things necessary in a.s.saying, and that he should close the doors of the room in which the a.s.say furnace stands, lest anyone coming at an inopportune moment might disturb his thoughts when they are intent on the work. It is also necessary for him to place his balances in a case, so that when he weighs the little b.u.t.tons of metal the scales may not be agitated by a draught of air, for that is a hindrance to his work.

[Ill.u.s.tration 223a (m.u.f.fle Furnace): Round a.s.say furnace.]

[Ill.u.s.tration 223b (m.u.f.fle Furnace): Rectangular a.s.say furnace.]

[Ill.u.s.tration 224 (m.u.f.fle a.s.say Furnace): A--Openings in the plate.

B--Part of plate which projects beyond the furnace.]

Now I will describe the different things which are necessary in a.s.saying, beginning with the a.s.say furnace, of which one differs from another in shape, material, and the place in which it is set. In shape, they may be round or rectangular, the latter shape being more suited to a.s.saying ores. The materials of the a.s.say furnaces differ, in that one is made of bricks, another of iron, and certain ones of clay. The one of bricks is built on a chimney-hearth which is three and a half feet high; the iron one is placed in the same position, and also the one of clay.

The brick one is a cubit high, a foot wide on the inside, and one foot two digits long; at a point five digits above the hearth--which is usually the thickness of an unbaked[2] brick--an iron plate is laid, and smeared over with lute on the upper side to prevent it from being injured by the fire; in front of the furnace above the plate is a mouth a palm high, five digits wide, and rounded at the top. The iron plate has three openings which are one digit wide and three digits long, one is at each side and the third at the back; through them sometimes the ash falls from the burning charcoal, and sometimes the draught blows through the chamber which is below the iron plate, and stimulates the fire. For this reason this furnace when used by metallurgists is named from a.s.saying, but when used by the alchemists it is named from the wind[3]. The part of the iron plate which projects from the furnace is generally three-quarters of a palm long and a palm wide; small pieces of charcoal, after being laid thereon, can be placed quickly in the furnace through its mouth with a pair of tongs, or again, if necessary, can be taken out of the furnace and laid there.

The iron a.s.say furnace is made of four iron bars a foot and a half high; which at the bottom are bent outward and broadened a short distance to enable them to stand more firmly; the front part of the furnace is made from two of these bars, and the back part from two of them; to these bars on both sides are joined and welded three iron cross-bars, the first at a height of a palm from the bottom, the second at a height of a foot, and the third at the top. The upright bars are perforated at that point where the side cross-bars are joined to them, in order that three similar iron bars on the remaining sides can be engaged in them; thus there are twelve cross-bars, which make three stages at unequal intervals. At the lower stage, the upright bars are distant from each other one foot and five digits; and at the middle stage the front is distant from the back three palms and one digit, and the sides are distant from each other three palms and as many digits; at the highest stage from the front to the back there is a distance of two palms, and between the sides three palms, so that in this way the furnace becomes narrower at the top. Furthermore, an iron rod, bent to the shape of the mouth, is set into the lowest bar of the front; this mouth, just like that of the brick furnace, is a palm high and five digits wide. Then the front cross-bar of the lower stage is perforated on each side of the mouth, and likewise the back one; through these perforations there pa.s.s two iron rods, thus making altogether four bars in the lower stage, and these support an iron plate smeared with lute; part of this plate also projects outside the furnace. The outside of the furnace from the lower stage to the upper, is covered with iron plates, which are bound to the bars by iron wires, and smeared with lute to enable them to bear the heat of the fire as long as possible.

As for the clay furnace, it must be made of fat, thick clay, medium so far as relates to its softness or hardness. This furnace has exactly the same height as the iron one, and its base is made of two earthenware tiles, one foot and three palms long and one foot and one palm wide.

Each side of the fore part of both tiles is gradually cut away for the length of a palm, so that they are half a foot and a digit wide, which part projects from the furnace; the tiles are about a digit and a half thick. The walls are similarly of clay, and are set on the lower tiles at a distance of a digit from the edge, and support the upper tiles; the walls are three digits high and have four openings, each of which is about three digits high; those of the back part and of each side are five digits wide, and of the front, a palm and a half wide, to enable the freshly made cupels to be conveniently placed on the hearth, when it has been thoroughly warmed, that they may be dried there. Both tiles are bound on the outer edge with iron wire, pressed into them, so that they will be less easily broken; and the tiles, not unlike the iron bed-plate, have three openings three digits long and a digit wide, in order that when the upper one on account of the heat of the fire or for some other reason has become damaged, the lower one may be exchanged and take its place. Through these holes, the ashes from the burning charcoal, as I have stated, fall down, and air blows into the furnace after pa.s.sing through the openings in the walls of the chamber. The furnace is rectangular, and inside at the lower part it is three palms and one digit wide and three palms and as many digits long. At the upper part it is two palms and three digits wide, so that it also grows narrower; it is one foot high; in the middle of the back it is cut out at the bottom in the shape of a semicircle, of half a digit radius. Not unlike the furnace before described, it has in its forepart a mouth which is rounded at the top, one palm high and a palm and a digit wide.

Its door is also made of clay, and this has a window and a handle; even the lid of the furnace which is made of clay has its own handle, fastened on with iron wire. The outer parts and sides of this furnace are bound with iron wires, which are usually pressed in, in the shape of triangles. The brick furnaces must remain stationary; the clay and iron ones can be carried from one place to another. Those of brick can be prepared more quickly, while those of iron are more lasting, and those of clay are more suitable. a.s.sayers also make temporary furnaces in another way; they stand three bricks on a hearth, one on each side and a third one at the back, the forepart lies open to the draught, and on these bricks is placed an iron plate, upon which they again stand three bricks, which hold and retain the charcoal.

The setting of one furnace differs from another, in that some are placed higher and others lower; that one is placed higher, in which the man who is a.s.saying the ore or metals introduces the scorifier through the mouth with the tongs; that one is placed lower, into which he introduces the crucible through its open top.

[Ill.u.s.tration 227 (Crucible a.s.say Furnace): A--Iron hoop. B--Double bellows. C--Its nozzle. D--Lever.]

In some cases the a.s.sayer uses an iron hoop[4] in place of a furnace; this is placed upon the hearth of a chimney, the lower edge being daubed with lute to prevent the blast of the bellows from escaping under it. If the blast is given slowly, the ore will be smelted and the copper will melt in the triangular crucible, which is placed in it and taken away again with the tongs. The hoop is two palms high and half a digit thick; its diameter is generally one foot and one palm, and where the blast from the bellows enters into it, it is notched out. The bellows is a double one, such as goldworkers use, and sometimes smiths. In the middle of the bellows there is a board in which there is an air-hole, five digits wide and seven long, covered by a little flap which is fastened over the air-hole on the lower side of the board; this flap is of equal length and width. The bellows, without its head, is three feet long, and at the back is one foot and one palm wide and somewhat rounded, and it is three palms wide at the head; the head itself is three palms long and two palms and a digit wide at the part where it joins the boards, then it gradually becomes narrower. The nozzle, of which there is only one, is one foot and two digits long; this nozzle, and one-half of the head in which the nozzle is fixed, are placed in an opening of the wall, this being one foot and one palm thick; it reaches only to the iron hoop on the hearth, for it does not project beyond the wall. The hide of the bellows is fixed to the bellows-boards with its own peculiar kind of iron nails. It joins both bellows-boards to the head, and over it there are cross strips of hide fixed to the bellows-boards with broad-headed nails, and similarly fixed to the head. The middle board of the bellows rests on an iron bar, to which it is fastened with iron nails clinched on both ends, so that it cannot move; the iron bar is fixed between two upright posts, through which it penetrates. Higher up on these upright posts there is a wooden axle, with iron journals which revolve in the holes in the posts. In the middle of this axle there is mortised a lever, fixed with iron nails to prevent it from flying out; the lever is five and a half feet long, and its posterior end is engaged in the iron ring of an iron rod which reaches to the "tail" of the lowest bellows-board, and there engages another similar ring. And so when the workman pulls down the lever, the lower part of the bellows is raised and drives the wind into the nozzle; then the wind, penetrating through the hole in the middle bellows-board, which is called the air-hole, lifts up the upper part of the bellows, upon whose upper board is a piece of lead, heavy enough to press down that part of the bellows again, and this being pressed down blows a blast through the nozzle.

This is the principle of the double bellows, which is peculiar to the iron hoop where are placed the triangular crucibles in which copper ore is smelted and copper is melted.

[Ill.u.s.tration 228 (m.u.f.fles): A--Broad little windows of m.u.f.fle.

B--Narrow ones. C--Openings in the back thereof.]

I have spoken of the furnaces and the iron hoop; I will now speak of the m.u.f.fles and the crucibles. The m.u.f.fle is made of clay, in the shape of an inverted gutter tile; it covers the scorifiers, lest coal dust fall into them and interfere with the a.s.say. It is a palm and a half broad, and the height, which corresponds with the mouth of the furnace, is generally a palm, and it is nearly as long as the furnace; only at the front end does it touch the mouth of the furnace, everywhere else on the sides and at the back there is a s.p.a.ce of three digits, to allow the charcoal to lie in the open s.p.a.ce between it and the furnace. The m.u.f.fle is as thick as a fairly thick earthen jar; its upper part is entire; the back has two little windows, and each side has two or three or even four, through which the heat pa.s.ses into the scorifiers and melts the ore. In place of little windows, some m.u.f.fles have small holes, ten in the back and more on each side. Moreover, in the back below the little windows, or small holes, there are cut away three semi-circular notches half a digit high, and on each side there are four. The back of the m.u.f.fle is generally a little lower than the front.